Excluding diapers, there are currently two solutions regarding urine management in orbit. The first solution is to vent the urine overboard, which has been employed on the Shuttle Orbiter and other prior United States spaceships. The second solution is to stow the urine on board, which has been employed in the Soviet/Russian Soyuz spaceship and the International Space Station. Stowing urine on board has become the desired approach for new spacecraft.
In spacecraft urinal systems, where urine is collected and stored over long periods of time, the pretreatment of urine is of eminent importance. It has been found that pretreatment serves to increase the reliability of such systems and serves to reduce the amount of maintenance time for cleaning and repairing system hardware. In particular, pretreatment of urine is required in spacecraft urinal systems to control odors, fix urea, and control microbial growth. In addition, pretreatment is required to reduce or eliminate fouling of the hardware and plumbing with urine precipitates and thereby assure long term use of urine collection equipment.
Typically urine contains about 96 percent water and about 4 percent solids in solution. About half of the solids consist of urea, (NH2)2 CO, while the remainder of the solids include chloride, sodium, potassium, nitrogen, ketosteroids, phosphate, sulfur, ammonia, creatinine, and uric acid. Without some form of pretreatment, many of the constituents of urine will decompose at room temperature and will become contaminated with bacteria, which will result in further decomposition. In particular, urea decomposes resulting in the formation of ammonia and carbon dioxide, and a significant amount of solids precipitate out of solution resulting in the fouling of urine collection equipment. Additionally, the evaporation of water in urine, resulting from air entrainment therein, facilitates the precipitation of urine salts.
Historically, the space shuttle has used a shuttle urine pretreatment assembly (SUPA) to handle pretreating the urine. However, the shuttle urine pretreatment assembly requires replacing an entire section of a urine inlet hose on a daily basis. Depending on the length of the mission, the spacecraft must carry and store multiple shuttle urine pretreatment assemblies for the crew members. The shuttle urine pretreatment assemblies are heavy and require a significant amount of space for storage. Therefore, there is a need for a light weight shuttle urine pretreatment assembly that can be easily stored and replaced.